What is Intermittent Fasting (IF)?

Intermittent fasting (IF) is a broader term encompassing various eating patterns that involve alternative periods of eating and fasting. IF has gained significant attention recently for its potential benefits in weight loss, improved health, and overall well-being.

Many diets focus on what to eat. However, IF is all about when to eat. IF patterns can include:

  • Alternate-day fasting: Fasting every other day.
  • 5:2 diet: Eating normally for five days a week and consuming significantly fewer calories (500-600 calories per day) for the remaining two days.
  • 16:8 method: Fasting for 16 hours and eating during an 8-hour window in the 24 hours.
  • One Meal a Day (OMAD): Eating once in 24 hours.

The 16:8 and OMAD are also known as time-restricted feeding.

What are the Benefits of IF?

Research shows that restricting calories over a lifetime remarkably slows aging and increases animal lifespan. However, whether IF is definitively associated with increased human longevity is unknown.

Many of IF's benefits are not just due to reduced free radical production or weight loss. Instead, IF elicits evolutionarily conserved, adaptive cellular responses between and within the organs that regulate glucose, increase stress resistance and suppress inflammation.

Health benefits of intermittent fasting

During fasting, cells activate pathways that enhance intrinsic defense against metabolic and oxidative stress and those that remove injured or damaged molecules.

IF protects against many chronic diseases such as type 2 diabetes, heart disease, age-related neurodegenerative diseases such as dementia, inflammatory bowel diseases, auto-immune diseases, and many cancers. Some of the key benefits are:

  • Weight loss: IF can help reduce overall calorie intake and boost metabolism, making it an effective weight loss tool.
  • Improved insulin sensitivity: IF can lower blood glucose and fasting insulin levels and reduce insulin resistance, protecting against pre-diabetes and developing Type 2 diabetes.
  • Cardiovascular disease: IF may protect heart health by reducing risk factors such as blood pressure, cholesterol, and inflammation.
  • Brain Health: IF enhances brain function by reducing oxidative stress and inflammation and promoting the growth of new nerve cells as it stimulates the production of a hormone called brain-derived neurotrophic factor (BDNF), which helps improve mental clarity, memory, and problem-solving skills. 
  • Cellular repair: Fasting triggers autophagy, which helps remove damaged cells and promotes cellular repair.
  • Reduced inflammation: IF can decrease inflammation linked to various chronic diseases (e.g., arthritis, multiple sclerosis, asthma).

Watch Swami Mukundananda ji to hear his perspectives on intermittent fasting.

How does IF work?

Glucose and fatty acids are the primary energy sources for the cells in our body. After a meal, glucose is used for energy, and the fat is stored in the adipose (fatty) tissue as triglycerides.

In a fed state, the insulin levels increase proportionately to the blood glucose levels, driving the blood glucose inside the cells. Insulin also inhibits lipolysis, which means that fat stores in our body cannot be broken down during the fed state and cannot be used for energy.

A metabolic switch occurs in our body during the switch from a fed to a fasting state.

Since blood glucose levels are low during fasting, plasma insulin levels are suppressed. Low insulin and glucose levels result in the release of glucagon, which binds with the triglycerides in the adipose tissue and breaks them into glycerol and fatty acids, which are then used for energy. The liver converts fatty acids to ketone bodies, a significant energy source for many tissues, especially the brain. Glycerol and fatty acids can also generate glucose through a process called neo-glucogenesis.

Ketone bodies are not just a fuel source used during fasting but potent signaling molecules that significantly benefit cell and organ function. The longer the IF, the greater the production of fatty acids and ketone bodies.

Our body stores over 100,000 calories as fat in the adipose tissue. However, we do not tap into that internal energy source because we consume exogenous calories, which increase insulin levels and turn off lipolysis for energy sources.

This is one of the reasons why diabetes and obesity are highly prevalent in our society. Excess calorie consumption and persistent hyperinsulinemia result in cellular insulin resistance and Type 2 diabetes. IF reverses this cascade.

Research shows that losing a modest 5% to 7% of body weight carries numerous health benefits in obese individuals, as it reduces the risk of dyslipidemia, hypertension, and diabetes mellitus. For example, in one study of patients with impaired glucose tolerance, losing 7% of body weight was associated with a 58% reduction in the risk of developing type 2 diabetes!

Is IF safe?

Some people use IF for weight management, while others use it to address chronic diseases such as diabetes, high cholesterol, heart disease, or arthritis. However, IF isn’t for everyone. Before you try IF, check with your physician. Some people should not do IF:

  • Children and teens under the age of 18 as it may interfere with their growth.
  • Women who are pregnant or breastfeeding.
  • People with type 1 diabetes who take insulin without physician supervision.
  • Those with a history of eating disorders such as anorexia nervosa and bulimia.
  • Those who are underweight and malnourished.
  • People not in the above categories who can do IF safely can continue the regimen indefinitely.

How to begin IF?

Starting IF involves gradually incorporating fasting periods into our work life. We can begin with shorter fasting windows and progressively increase them as we become more comfortable.

We must focus on consuming nutrient-dense foods during our eating window during IF. Prioritize whole, unprocessed foods like vegetables, lean proteins, whole grains, healthy fats, and fruits.

During IF, the body excretes excess water. Therefore, drink plenty of water to stay hydrated. People often confuse thirst with hunger and eat food instead of drinking water.

If you're new to IF, starting with the 16:8 method of time-restricted feeding is relatively easy.

It is important not to overeat during the eating window. Overall, IF must be used to achieve calorie restriction if weight loss is the goal. Consuming excess calories during the feeding window will be counterproductive.

If you’re a woman, the week before the period can be challenging due to premenstrual syndrome, which causes food cravings, mood swings, and low energy. In these situations, a shorter 12-hour fast would be more tolerable than a 14- or 16-hour fast.

Strenuous exercise and longer fasting times do not go well together. Pick a schedule based on your workout intensity and duration and perform a workout preferably during your feeding window or shortly before the fast begins.

Table 1 outlines a suggested plan for starting 16:8 time-restricted feeding.

Watch Swami Mukundananda ji describe the science of a healthy diet.

What is the difference between IF and calorie restriction?

IF and calorie restriction can reduce calorie intake and promote weight loss. However, they differ in their approach.

IF involves cycling periods of eating and fasting. Calorie restriction involves consuming fewer calories during each meal. Calorie restriction focuses on what we eat and how much we eat.  It doesn’t focus on when we eat. Calorie restriction involves portion control, choosing low-calorie foods, and limiting unhealthy foods and beverages.

A critical difference between IF and a calorie-restricted diet is that our metabolism will tend to slow down during a calorie-restricted diet as our body tries to adapt to fewer calories by slowing down the metabolism to conserve energy; however, during IF, the metabolism does not slow down but instead increases due to switching from glucose to fat as a source of energy, which is induced by glucagon and other adrenergic hormones.

Watch Swami Mukundananda ji on the best time to eat during the day.

What are some of the advantages of IF?

  • IF is simple
  • IF is free
  • IF is convenient
  • IF is powerful
  • IF is flexible
  • IF works with any diet

What are some of the common concerns with IF?

  • Hunger: The truth is hunger does not persist and comes in waves. So, if we can tolerate a little hunger, it will pass. As the body becomes accustomed to fasting, it starts to burn its stores of fat, which helps suppress appetite.
  • Dizziness: This is most likely due to dehydration. Be sure to drink plenty of water; if you’re low on salt, add sea salt to water. Another possibility is that your blood pressure is too low, particularly if you’re taking medications for hypertension. Speak to your physician about adjusting your medication.
  • Headaches: This is a common symptom in the first week of fasting and usually occurs due to carbohydrate withdrawal and dehydration. It is also thought to occur due to transitioning from a high-salt diet to a low-salt one. It is generally temporary and will resolve on its own.
  • Constipation: Bowel movements typically decrease during a fast simply because of less food intake. If you are not experiencing discomfort, you don’t need to worry about reduced bowel movements. However, increasing fiber intake, fruits, and vegetables during the non-fasting period may help with constipation.
  • Heartburn: To prevent heartburn after a fast, avoid eating large meals. This usually resolves without any treatment after the first week. Avoid lying down immediately after a meal; stay upright for at least half an hour after meals.
  • Muscle cramps: Low magnesium may cause muscle cramps. You may take an over-the-counter magnesium supplement. You may also soak in Epsom salts, which are magnesium salts.

Resources

1.        Rafael de Cabo, and Mark P. Mattson. Effects of Intermittent Fasting on Health, Aging, and Disease. N Engl J Med 2019;381:2541-2551

2.        Complete Guide To Fasting: Heal Your Body Through Intermittent, Alternate-Day, and Extended Fasting” by Dr. Jason Fung and Jimmy Moore

3.        Navratri Fast: Essential Tips for a Healthy and Spiritual Balance.

4.        Nutrition and healthy living.